I propose to continue our studies which show that histones 1 and 5 (H1, H5) can bind tightly to mononucleosomes in the absence of linker DNA, and which suggest that the conformations of H1-containing and H1-lacking nucleosomes are different from one H1-containing and H1-lacking particles to test the idea that they are conformationally dissimilar. Sensitivity of the two classes of particles to DNAase I digestion will also be compared as a conformational probe, and the subnucleosomal digestion pattern obtained with H1-containing core particles will be assayed to determine whether their structure is native. Preparative amounts of H1-containing core particles will be made for further conformational studies. Finally, radioactive DNA complementary to globin m-RNA will be bound to DNA obtained from H1- and H5-containing and H1- and H5-lacking nucleosomes from chick erythrocytes to test the possibility that the latter class of particles contains the activated genes. Since other studies suggest that active and inactive nucleosomes are conformationally dissimilar, the H1-related differences probed in this study could be implicated in the mechanism of eukaryotic gene control.